Logic Program Development Based on Typed Moded Schemata and Data Types

Abstract

The main contribution of the thesis is to develop a comprehensive framework for developing logic programs using five program schemata and some basic data types, and to evaluate its suitability for developing sizable programs. The schemata are intended to capture design decisions made by a programmer during top-down refinement of a predicate. The schemata are completely independent from the data types, and have associated types and modes. The method of construction is to start from an initial typed moded call, and proceed using precisely defined refinement operations until primitive data type operations are introduced. It is shown that the construction method produces programs that are polymorphic many-sorted formulas, and that computations using the programs cannot result in type or mode errors. The framework is compared with previous schema-based program development methods from the literature, and we argue that this method is better suited to the development of non-trivial programs, and is more amenable to computerised support. The introduction of types and modes into schemata is a significant addition, not previously reported. An approach to program verification is also introduced, in which the proof of correctness of a program is built from proof schemata corresponding to the program schemata used in the design of the program. Finally an implementation of the system is described and its use is illustrated on some sizable programs. The implementation incorporates a static analysis algorithm for checking the validity of the modes during the development of the program.